After the order to bail out is given, Colonel Gallagher leaves the cockpit wearing his uniform hat. As he bails out of the B-17, he is wearing a leather aviators cap. After he lands, after parachuting down, he has no hat or leather cap.
Col. Gallagher is seen at the end flying a combat mission after being returned to England by the French Underground. In actuality, Col. Gallagher would not have been allowed to fly combat missions again over Europe in case he was shot down again. He knew too much about the Underground and could possibly have divulged important information about the Underground if captured. This is why Karl was posing as a deserter to get that information about the Underground's networks.
When Col. Gallagher's plane is shown crashing, there is a CG-4 glider in the foreground. Since this was a daytime shot, it is actually footage of a C-47 crashing after being shot down during Operation Market Garden, the attempt liberate the Netherlands and cross the Rhine river in the fall of 1944.
The American Flag patch on actor Chris Robinson's flight jacket has 50 stars.